# username = input('what is name?')
# print(username)

import json
filename = 'username.json'

try:
    with open(filename) as f_obj:
        username = json.load(f_obj)
except FileNotFoundError:
    username = input('what is name?')
    with open(filename,'w') as f_obj:
        json.dump(username,f_obj)
        print('you are regist success')
else:
    print('welcome back,' + username)